Structure of improved pneumatic gripper assemblies

ABSTRACT

The invention relates to a pneumatic gripper assembly structure which comprised a supporting body ( 11, 111 ) composed of at least two wall elements or symmetrical half-shells ( 15, 115 ), realized and finished individually using a forming process and then put together to form a single body capable of receiving, supporting and guiding other structural and functional components of the gripper assembly. The complementary wall elements or half-bodies are produced using die-casting, sintering or forging techniques with material compatible for said processes and have means for housing jaws and a drive piston of the gripper.

FIELD OF INVENTION

This invention concerns pneumatic gripper assemblies in general used forsecuring items being machined and/or for automatic manipulation, andrefers in particular to improved components for setting up suchassemblies.

State of the Art

Both linear and angular pneumatic grippers, of the type taken intoconsideration here, are well known as regards to structure andfunctioning. They can be of different shapes, sizes and capacity, buteach one is made up essentially of a supporting body, a simple ordouble-acting piston, moving either in a chamber or jacket in said body,and two jaws supported and guided in the body, working in conjunctionwith the piston, moving straight or at an angle in opposite directionsin response to the alternating movements of the piston and supportingtwo item gripper jaw.

According to the known techniques, the components of said pneumaticgripper assemblies are machined on tool machines. In particular the bodyof a pneumatic gripper assembly is enbloc and is made starting from anunfinished piece, machined and bored as required to receive theoperating components and the accessories which make up the gripperassembly.

As the technicians in this sector are well aware, the constructionprocess of similar gripping assemblies is extremely laborious andpainstaking due to the machining and operating times needed and oftenbecause of the fine tolerances required. The need to find innovativemethods to produce pneumatic gripper assemblies of the type subject ofthis invention which are simpler and less costly, without having tomachine or at least which reduce the machining operations greatly stemsfrom this requirement.

On the other hand, forming techniques of elements such as die-casting,sintering, and forging which enable the production of items, evenfinished, with relatively complex shapes, with fine tolerances orhowever with a high level of precision, both as regards to size andsurface finishing, and with the possibility of surface treatments,depending on necessity, at least in the case of sintered items, are wellknown.

These forming techniques, although well established in practice, havenever been adopted in the gripper assembly manufacture field or if usedonly limited to basic components also because the configuration of theelements of these grippers, used in the traditional way, do not enableit.

OBJECTIVES AND SUMMARY OF THE INVENTION

This invention has been conceived to meet the above-mentionedrequirement and to be able to take good advantage of the formingtechniques of the items referred to above also in the manufacture ofpneumatic gripper assemblies and to create the conditions to eliminateor at least minimise machining and assembling times and costs.

It in fact an objective of this invention to present and supplycomponents for setting up pneumatic gripper assemblies, designed so asto be able to be produced using one or the other of the formingtechniques for die-casting, sintering and forging and then assembledusing simple fixing systems.

Another objective of the invention is the realisation of pneumaticgripper assemblies, each one made up of a limited number of pre-formedelements capable of fitting complementarily one with the other and withinserted auxiliary elements, ensuring the functionality of the resultinggroup improving in fact performance and life.

A further objective of the invention is to supply a linear or angularpneumatic gripper assembly which is easy to set up using a “sandwich”type assembly of the supporting and functional components.

To achieve the invention, the supporting body of a gripper assembly wasdisassembled into complementary parts to be produced separately usingone of the above said techniques and then to be assembled to form onesolid group capable of receiving, supporting and guiding otherstructural and functional components of the gripper.

The structure of a pneumatic gripper assembly according to the inventionis substantially the one conforming with claim 1.

BRIEF DESCRIPTION OF DRAWINGS

Greater details of the invention will become more evident in thefollowing description made with reference to the indicative andnon-limiting drawings enclosed, in which:

FIG. 1 is an exploded view in prospective of the components for theconstruction of a linear pneumatic gripper assembly;

FIG. 2 is an enlarged view of a half-body for the formation of thegripper assembly body;

FIG. 3 is a linear pneumatic gripper assembly with the components inFIG. 1 partially assembled;

FIG. 4 is a view in prospective of the linear pneumatic gripperassembly, completed assembled;

FIG. 5 is a longitudinal cross-section of the assembled gripper unit indirection of arrows V-V in FIG. 6;

FIG. 6 is a cross-section of the assembled gripper in the direction ofarrows VI-VI in FIG. 5;

FIG. 7 is a further cross section of the gripper assembly on a levelwith the two anchoring bolts;

FIG. 8 is an exploded view in prospective of the components of a linearpneumatic gripper assembly in compliance with a variation inconstruction;

FIG. 9 is a partially assembled linear pneumatic gripper assembly asshown in FIG. 8;

FIG. 10 is a view in prospective of the completely assembled linearpneumatic gripper assembly;

FIG. 11 is an exploded view of the components of an angular pneumaticgripper assembly;

FIG. 12 is a view in prospective of the fully assembled angularpneumatic gripper assembly.

DETAILED DESCRIPTION OF THE INVENTION

Both the linear and angular pneumatic gripper assembly representedcomprises a supporting body 11, an alternating piston 12 moving in saidbody, a drive system 13 associated with the piston and two jaws 14driven by the piston, moving in opposite directions by means of thedrive system 13 and each one can be equipped with jaw shoes not shown.The only difference between the two types of pneumatic grippers is thatthe jaws in the linear grippers are subjected to rectilinear movementsin opposite directions, whereas in the angular grippers the jaws turneach one on a pin, performing angular movements in opposite directionsin response to the movements of the piston.

According to a construction method as illustrated in FIGS. 1-7, thesupporting body 11 is made up of two exactly equal elements or symmetrichalf-bodies or shells 15. They therefore can be made advantageously fromthe same mould, using die-casting, sintering or a forging systems in anyappropriate material.

The two half-bodies 15 are placed one facing the other, they fit oneinto the other and are fixed together. Each one has a support plane 16from which an intermediate part rises 17, with two sides 17′, which istopped by a straight flat section 18.

The supporting plane 16 forms a support base 16′ and, on the twoopposite sides it has two ears 19 protruding from the intermediatesection 17 each one having a half hole 20 perpendicular to the supportbase 16′ and open towards the opposite semi-body. At the height of eachhalf hole 20 a semi-hexagonal recess 20′ can be formed.

A cylindrical cavity 21 has been machined at the height of theintermediate section 17, the axis of which is parallel to the supportbase 16′. The cavity 21 is closed by a bottom wall 22 in which a hole22′ is provided and opens towards the half-body opposite. In the toppart of cavity 21, there is a slide surface 23 at one end of which, onthe open side of the cavity itself, has been formed a semi-slot 23′. Onthe parts opposite to cavity 21, on a parallel with its axis, holes 24have been provided, for example two on each side placed symmetrically toeach other. Preferably, centring protrusions 24′ are provided at theheight of the two said diagonally opposite holes 24, on the open side ofcavity 21, whereas at the height of the other holes there arecomplementary housings 24″. On each side 17′ of the intermediate section17 a duct 25 is provided which runs parallel to the axis of cavity 21.

The top part 18 of the half-body 15 is at a right angle to thecylindrical cavity 21 axis. A flexing groove 26 is provided externally,between the top part 18 and the intermediate part 17. Two or moretransversal holes 27 are provided in the top part 18 on at one leveland, above these, in the internal face of the part itself a longitudinalgroove divided by an intermediate baffle has been formed. A tongue 29has been provided in a central position on the top side of part 18facing inwards, that is to say towards, a similar tongue on the oppositehalf-body.

The drive system 13 as well as the jaws can also be produced using thesame forming techniques used in making the half-bodies 15.

In particular, the drive system 13 has a central hole 30 and, on theopposite sides to the latter, two slots 31 in a V formation.

The jaws 14 are the identical and can be made from the same mould. Eachjaw 14 has a connecting pin 32 for coupling with the drive system 13,transversal holes 33 at the top, and on each side a groove 35 which willbe at the same height and opposite the groove 28 on the internal face ofthe top part 18 of the adjacent half-body.

When setting up a gripper assembly, the two elements or half-bodies 15are placed one in front of the other and bolted tightly together usingbolts 35 inserted in the transversal holes 24 in the sides of thecylindrical cavity 21 and other bolts 36 inserted in the transversalholes 27 at the height of the top part 18. When the two half-bodies areunited, their cavities 21 are in line and form a chamber 37—FIG. 5, 6—inwhich the piston 12 driving the jaws 14 is housed. If the piston isdouble-acting, the piston 12 is driven by a fluid under pressure,delivered/discharged alternately in the chamber 37 by means of ductsconnected to the bottom walls of the cavity at the same level as holes22′. If the piston is single-acting, the piston is driven in onedirection by the fluid fed to chamber 37 and return is spring driven.

When the half-bodies are assembled together, the side ears form withthere half-holes, holes for the anchoring screws 38 of the gripper uniton the support. Advantage only each of said holes, thanks to thesemi-hexagonal hollows 20′, can house and hold a nut 39 which means thatthe respective anchoring screws can be applied both from the top orbottom according to needs—FIG. 5.

The driver 13 is positioned on the slide surface 23 above the pistonchamber 12 and is connected to the latter by means of a pin 40 insertedinto its central hole 30 and passing through to insert into the slotformed by the half-slots 23′ of the two united half-bodies.

The top facing parts 18 of the two half-bodies 15 form a guide housing41, and the jaws 14 are placed in said housing together with interposedball bearings 42. Each jaw is associated, through its respectiveconnecting pin 32, with a slot 31 of the driver 13 so that the jaws movein opposite directions in response to the alternating movements of thepiston 12.

The bearings 42 are positioned between the internal grooves 28 of thetop part 18 of the half-bodies and the lateral grooves 34 of the jawsthemselves. Furthermore, by tightening or loosening the anchoring screws36 passing through the transversal holes 27 in the top parts of thehalf-bodies and thanks to the flexing groove 26 along the base of eachof said parts it is possible to calibrate their nearness in order toestablish a correct preload of the assembled functional elements and tobe able to recover play and coupling wear.

Jaws shoes can be fixed to the holes 33 of the jaws 14 as required. Thetop tongues 29 of the top part of the half-bodies, when brought togetherform a protective portion—FIG. 4—suitable for stopping dust or dirtentering the space between the grippers 14. The lateral ducts 25 of thehalf-bodies 15 can be used to apply accessories to the gripperassemblies, such as for example end of stroke sensors and so on.

In compliance with the invention and according to a another method ofconstruction illustrated in FIGS. 8-12, the gripper assembly has asupporting body 111 made up of several complementary parts which includetwo opposite wall elements 115 and two side elements 116, all thoseelements being formed by die-casting, sintering or forging of anyappropriate material.

The two wall elements or cheek 115 are the identical, therefore can bemade from the same mould. They are positioned one facing the other, andeach one has a base plane 117, at least one lower couple of transversalholes 118 just above the base plane and at least one higher couple oftransversal holes 119 at a different level.

The base plane 117 has two semi-holes 120 perpendicular to each of itsends, one facing inwards and the other facing outwards in relation tothe body.

Longitudinally, the internal face of each cheek 115, the one facing theother cheek, has a recess 121 which may be cylindrical, but preferablywith faceted surfaces, that is polygonal, viewed in cross-section. Eachcheek 115 has a groove 122 on the internal surface which runs parallelto the longitudinal recess 121 above it and closed at both ends.

Longitudinally, the external face of each cheek 115 has a semi-duct 123at one level and a flexing groove 124 at a higher level, between thebottom and top couple of holes 118, 119. On the top of each cheek 115there is a central positioned recess 125 with a coupling lug 126.

The two side elements 116 are the identical, therefore can be made fromthe same mould. Each one is positioned externally and positioned againsta relative wall element or cheek 115 and is lower in height to the levelof the top couple of holes 119 of the cheeks.

Each side element has a base plane 127 with two semi-holes 128 at itsends on the side facing towards the adjacent cheek, and above the baseplane, a couple of transversal holes 129 in line with the bottom coupleof holes 118 of the cheeks 115. In addition, on the internal face, theone facing the adjacent cheek, each side element has a complementarysemi-duct 130 running longitudinally and at the same level as theexternal semi-duct 123 of said cheek.

The external walls of the opposite wall elements or cheek 115 and theside elements 116 are screwed tightly together to form the supportingbody using bolts 118′, 119′ passing through the couple of transversalholes 118, 119 in line. Consequently, the semi-holes 120, 128 at theends of the base plane of the wall elements and the side elements formin combinations of two by two the holes of the gripper assemblyanchoring screws. The wall elements with the recesses 121 on theadjacent faces form a housing for two casings or cylinders 131 Whichdetermine two separate sleeves or chambers in which to house a piston112 with its opposite ends.

The casings or cylinders 131 can also be made using a forming andfinishing technique as used to make the wall and side elements. To benoted that the casings or cylinders 131 have a polygonal externalsurface which fit together with the one with the recesses 121 formingthe housing they fit into. In this way the casings or cylinders areprevented from turning without having to provide other additionalsystems. Furthermore, each casing or cylinder 131 has a tapered neck131′ in which an anchoring bolt 118′ passes which besides helping inassembling the body 11 helps to achieve axial blocking of the respectivecasing or cylinder without having to insert flanges or covers as arerequired in the known technique.

Ball bearing raceway retainers 132 are fitted into the grooves 122 inthe internal faces of the wall elements or cheek 115, which in lineargripper assemblies—FIGS. 8 and 9—act as linear guide bearings for themovements of the jaws 113.

These jaws 113, as is also the case for the jaws 113′ for an angularpneumatic gripper assembly, may also be achieved with one of theabovementioned forming techniques.

Both the jaws 113 for a linear gripper assembly and the oscillating jaws113′ for angular gripper assemblies are coupled to the alternatingpiston 112 in the known way. In the case of oscillating jaws 113,antifriction and protective lining elements 133 can be inserted betweenthe latter and the cheeks against penetration of dirt from outside.

The piston can be double-acting, in which case each casing or cylinderis connected to a source of fluid under pressure by means of a coupling131″, with alternating delivery/discharge of the fluid in the twosleeves.

The piston 112 can also be single-acting, in which case one of thechambers formed by the casings or cylinders 131 is fed/dischargedalternately by a fluid under pressure, while in the other chamber,between the latter and the piston, there will be a return spring, notshown.

Furthermore, in the top part of the wall elements, in line with thecentral recesses 125 a protection plate 134 suitable for preventing dustand dirt penetrating between jaws 113, 113′ is assembled and snap lockedthanks to the coupling lugs 126.

The adjacent semi-ducts 123 and 130 of each wall element or cheek 115and respective side element 116 forming together a duct along whichaccessories such as magnetic end of stroke sensors can be made availableand positioned.

In addition and worthy of note is that the casings or cylinders 131forming the chamber for the piston 112 are separated at an axis one fromthe other leaving a space between them which means a permanent ringmagnet 135 can be applied around the piston 112 moving with it which hasa greater bore than the external diameter of the piston itself. Withthis expedient, the magnet 135 is closer to the end of stroke magneticsensors which may be inserted and positioned along the external ducts ofthe body.

By tightening or loosening the anchoring screws 119′ passing through thetop couple of transversal holes 119 and thanks to the flexing groove 124along each wall element 115 it is possible to calibrate their nearnessof the wall elements order to establish a correct preload of theassembled functional elements and to be able to recover play andcoupling wear.

It consequently seems evident that a type of gripper assembly asdescribed here can be realised starting from a minimum number ofpre-formed components, which in substance do not require machining andwhich are undemanding to assemble using only anchoring screws.

1. A pneumatic gripper assembly structure including a supporting body, apiston moving alternately in a chamber of said body, and two jawssupported and guided in said body, associated with the piston, moving inopposite directions in response to the alternate movements of the pistonand having each jaw shoes characterized in that the supporting body (11,111) is composed of at least two wall elements or symmetricalhalf-shells (15, 115), realized and finished individually using aforming process and then put together to form a single body capable ofreceiving, supporting and guiding other structural and functionalcomponents of the gripper assembly, the complementary wall elements orhalf-bodies being produced using die-casting, sintering or forgingtechniques with material compatible for said processes.
 2. A pneumaticgripper assembly structure according to claim 1, wherein the body (11)is composed of two equal half-bodies (15) placed one facing the otherand coupled together by fixing bolts transversely oriented by thehalf-bodies themselves.
 3. A pneumatic gripper assembly structureaccording to claim 2, wherein each semi-body (15) has a supporting base(16) from which an intermediate part (17) rises topped by a rectilinearpart (18), wherein said supporting plane has on opposite sides, two ears(19) protruding from the intermediate part (17) each having a semi-hole(20′) open towards the half-body opposite, wherein on a level with saidintermediate part a cylindrical cavity (21) on a parallel axis with thesupporting base is formed said cavity being closed by a base wall (22)which has a through hole (22′) and open towards the half-body opposite,and having at the top a slide plane (23) with a half-slot at the end(23′) of the open side of the cavity itself, wherein from opposite sidesof said cavity (21), parallel to its axis, symmetrically positionedholes (24) are formed, wherein in the top part (18) two or moretransversal holes (27) are provided at one level and above these, in theinternal face of the part itself, a longitudinal grove (28), and inwhich with the half-bodies put together, the holes besides the cavityand on a level with the top part are designed to receive the anchoringbolts of the half-bodies, the cavities of the half-bodies are alignedforming a chamber (37) for the drive piston, and the top parts of thehalf-bodies form a housing and guide for the jaws and are fixed togetherby bolts screwed into the respective transversal holes.
 4. A pneumaticgripper assembly structure according to claim 3 wherein the longitudinalgroove (28) in the top part (18) of each half-body (15) is opposite asimilar groove (34) in the adjacent side of each jaw (14) to receiveball bearings for guiding and sliding of said jaws.
 5. A pneumaticgripper assembly structure according to claims claim 3, wherein a driver(13) has been positioned between the drive piston and the jaws, saiddriver resting on the slide plane (23) above the chamber for the pistonand being coupled, on one side, to with said piston by means of aconnecting pin (40) and, on the other part, to the jaws by means ofdiverging slots (31), each jaw having a bottom pin (32) engaged in oneof said slots.
 6. A pneumatic gripper assembly structure according toclaim 1, wherein a duct (25) for the application of accessory devices isformed in the opposite sides of the intermediate part of each half-body.7. A pneumatic gripper assembly structure according to claim 1, whereina flexing groove (26) to vary the grip of the jaws between the top partsand relatively to the guide bearings has been formed between theintermediate part and the top part of each half-body.
 8. A pneumaticgripper assembly structure according to claim 1, in which a nutassociated with an fixing screw of the gripper assembly to a support hasbeen inserted into the hole of each ear of the supporting base.
 9. Apneumatic gripper assembly structure according to claim 1, in which thetwo half-bodies have tabs (29) which overlap parts of the jaws.
 10. Apneumatic gripper assembly structure according to claim 1, wherein thebody (111) of which is composed up of two opposite, identical cheeks(115) placed on facing the other and of two identical side elements(116), each one associated with a cheek on the outside thereof, saidcheeks and side elements being joined together by anchoring boltstransversely oriented to the same.
 11. A pneumatic gripper assemblystructure according to claim 10, wherein each wall element (115) has abase plane (117), at least one couple of lower transversal holes (118)just above the base plane, at least another couple of holes (119) at adifferent height and some half-holes (120) along the longitudinal sidesof the base plane, at the end of the latter and wherein each side (116)has a base plane (127), at least two transversal holes (129), coincidingwith the lower couple of transversal holes (118) in the wall element,and two half-holes at the opposite ends of the base plane (127), saidtransversal holes in the wall and side elements destined to receive theanchoring bolts of the wall and side elements to form a solid body,whereas said semi-holes of the wall and side elements form holes for theanchoring screws of the gripper assembly to a support.
 12. A pneumaticgripper assembly structure according to claim 10, wherein each wallelement (115) has a longitudinal groove (122) in its internal face toreceive a jaws linear bearing guide and a recess (121) to definetogether with a recess in the opposite wall element a housing toreceive, when wall elements are assembled, two casings or cylinders(131) forming two chambers or housing sleeves and guides of two partsaxially opposite to the jaws alternate, drive piston.
 13. A pneumaticgripper assembly structure according to claim 12, wherein the surface ofsaid recesses and said casings or cylinders (131) are complementarilyfaceted to prevent rotation of the casings or cylinders, and where thecasings or sleeves are separated at an axis to leave an intermediatepart of the piston exposed in order to apply a ring magnet, this magnetcould possibly have a bigger bore than that of the piston.
 14. Apneumatic gripper assembly structure according to claims 10-13, whereineach casing or cylinder (131) has a tapered neck (131′), and throughwhich one of the anchoring bolts passes at a tangent in order to axiallyhold the casing or sleeve in said housing.
 15. A pneumatic gripperassembly structure according to claims 10-14, wherein each wall element(115) has a longitudinal flexing groove (124) in order to vary thetightening between the jaws and the guide bearings.